[Amps] Led display problem

[David Kirkby]

Patrick EGLOFF wrote:
> Hi All,
> I'm new on this list...
> 
> I'm planning to build a 2m amp with a 4CX1500B tetrode.
> I want it a bit state of the art and replace the meters with LED bars.
> 
> My design will be a cathode driven, DC grounded amplifier and i want to 
> monitor at least screen, grid and anode current and anode voltage.
> 
> The LM3914 input seems to be always referenced to ground. No problem to 
> measure the screen current for which a pole of the supply is grounded.
> 
> But a bit more difficult to measure the other currents and voltages for 
> which the reference et the cathode level.
> 
> Has anyone an idea how to do that, on a simple way ?
> 
> 73, Patrick TK5EP.
> http://tk5ep.free.fr

Personally I don't think bargraphs are as useful as analogue meters, 
but, if that is what you want, there are  few options.

1) You can easily use a small transformer to power the circuit. Rectify 
the secondary voltage and reference that where you want (within reason). 
The secondrary will not mind being at what voltage it is connected to 
with respect to the chassis (within reason). I'd not do it in the high 
voltage side of the anode though!!

2) Even easier, if you can find some surplus, small DC-DC converters. 
Again, these are often isolated to 1 kV or so. New they tend to be quite 
expensive.

-- 
Dr. David Kirkby,
G8WRB

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/